Field of the Invention
The present invention relates to a semiconductor device forming a three-level power converter in which a turnoff surge voltage is reduced by reducing an inductance component.
Background Art
A three-level power converter has been adopted as a power converter for converting direct-current power into alternating-current power or for converting alternating-current power into direct-current power. A three-level power converter can reduce waveform distortion in an alternating-current voltage and enables producing an acoustic noise/electrical noise reduction effect.
FIGS. 20 and 21 are circuit diagrams each showing a conventional three-level power converter. FIG. 20 shows a 4-in-1 module, while FIG. 21 shows a 2-in-1 module and a collector-common module.
External terminals P and N are connected to a high-voltage terminal and a low-voltage terminal, respectively, of a direct-current voltage source circuit in which direct-current voltage sources DV1 and DV2 are connected in series. An external terminal C is connected to a connecting point between the direct-current voltage source DV1 and the direct-current voltage source DV2. A switching element Q1 is connected between the external terminal P and an external terminal AC. A switching element Q2 is connected between the external terminal AC and the external terminal N. Switching elements Q3 and Q4 are connected in inverse series connection with each other as an AC switch unit between the external terminal C and the external terminal AC.
The device shown in FIG. 20 is formed by incorporating the switching elements Q1 to Q4 in one module M and connecting the module to the direct-current voltage source circuit. The device shown in FIG. 21 is formed by incorporating in a first module M1 the switching elements Q1 and Q2 forming a bridge unit, incorporating in a second module M2 the switching elements Q3 and Q4 forming the AC switch unit and connecting the first and second modules to the direct-current voltage source circuit (see, for example, International Publication No. WO 2010/146637).